In the past two weeks we heard extensive accounts from numerous abuse victims of former Penn State assistant coach Jerry Sandusky, who was convicted for sexually assaulting 10 boys over an approximately 15-year period. But what we didn’t hear was anything that might explain the behavior of a pedophile, especially one who, when confronted by one of the victim’s mother years ago, reportedly said, “I wish I could ask for forgiveness. I know I won’t get it from you. I wish I were dead.”

As defined by the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders IV-TR, pedophilia involves recurrent sexual attraction or behavior with prepubescent children (generally under age 13). The charges against Sandusky would fall within this definition — the victims who testified were usually 10 or 11 when the abuse began. Sandusky’s defense team argued that the “love letters” and other attention he paid to these boys were explained by histrionic personality disorder (HPD). People with HPD are prone to flirtatiousness, attention-seeking and emotionally manipulative behavior — they use their social skills and charm to get what they want from others but also may use dramatic moods to manipulate. Think Scarlett O’Hara from Gone with the Wind or pretty much all the characters on Will and Grace. However, people with HPD typically try to seduce same-age peers, not children. Whether Sandusky does or does not have HPD has little bearing on his behavior toward children, which represents a major deviation from normative sexual behavior.

In a study published in Biological Psychiatry, Martin Walter and his colleagues found that the hypothalamic regions of the brains of pedophiles, a region heavily involved in sexual identity and behavior, are not stimulated by erotic images of adults the way that nonpedophiliac brains are. Neurologically, pedophiles don’t identify adults as sexually attractive. Other brain-imaging works by James Cantor and colleagues published in the Journal of Psychiatric Research and Kolja Schiltz and colleagues writing in the Archives of General Psychiatryconfirm that pedophiles have impairments to brain structures involved in sexual development. Put simply, the brains of pedophiles are different from those of other adults.

However, it’s worth noting we don’t yet fully understand the origin of these brain differences. Although I think it unlikely, it is possible that they arise from pedophiliac interest rather than pedophiliac interest being the consequence of brain differences. Research by Ray Blanchard and colleagues published in the Archives of Sexual Behaviorfound that pedophiles report experiencing a higher number of head injuries, particularly before age 13. These reported head injuries were associated also with attention problems and at the very least suggest that pedophilia can be traced back to structural issues with the brain predating puberty, although it’s not yet certain whether the injuries in question led to sexual-development problems or whether problems in earlier neurodevelopment led to both pedophilia and accident proneness.

More research will continue to clarify the origins of a behavior that is extremely difficult for most of us to understand and is deeply repugnant. One common misconception is that victims of childhood sexual abuse are highly likely to later become abusers themselves. Most of the studies that supported this view were retrospective studies of offenders asking them whether they had been abused. The problem is that many perpetrators see claims of their own abuse as a potential mitigating factor that will lead to leniency. However, even such retrospective studies like one published in the British Journal of Psychiatry in 2001 find that the majority of abusers do not report having been abused themselves as children. And a longitudinal 2003 study, a better standard for assessing risk, made clear that the vast majority of sexual-abuse victims do not become abusers. Those few who did tended to experience other forms of neglect and violence within the family. The victim of sexual assault who is otherwise cared for by his or her family is highly unlikely to become a future predator. Like many abnormal behaviors, pedophilia likely stems from a biological predisposition combined with exposure to a harsh environment. Child abuse is horrific; but the fact that it doesn’t produce an endless chain of future abuse is something we can take small comfort in.